Degrees of separation for handling communications

ABSTRACT

A sender&#39;s degrees of separation from a recipient may be used to aid in spam filtering or to otherwise handle a communication. The “degrees of separation” represent a metric used to quantify whether/how the recipient is linked to the sender through intermediary people or other entities. For example, a recipient may know a first user (first degree of separation) and the first user may know a second user (second degree of separation) who knows the sender of an e-mail. In this case, the sender is separated from the recipient by two degrees of separation (by two other contacts). A level of “trust” or “legitimacy” about a sender&#39;s communication can be inferred by looking at whether the sender is linked to an intended recipient. Typically, user contact lists (e.g., address book, buddy list, and/or white list) are evaluated to determine the number of degrees (or hops) are required to link or relate two users.

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Application No.60/459,272, filed on Apr. 2, 2003, which is incorporated by reference.

TECHNICAL FIELD

This description relates to handling communications.

BACKGROUND

With the advent of the Internet and a decline in computer prices, manypeople are communicating with one another through computersinterconnected by networks. A number of different communication mediumshave been developed to facilitate such communications. One prolificcommunication medium is electronic mail (e-mail).

Unfortunately, because the costs of sending e-mail are relatively low,e-mail recipients are being subjected to mass, unsolicited, commerciale-mailings (colloquially known as e-mail spam or spam e-mail). These areakin to junk mail sent through the postal service. However, because spame-mail requires neither paper nor postage, the costs incurred by thesender of spam e-mail are quite low when compared to the costs incurredby conventional junk mail senders. Due to this and other factors, asignificant amount of spam e-mail is sent to e-mail users on a dailybasis.

Spam e-mail impacts both e-mail users and e-mail providers. For ane-mail user, spam e-mail can be disruptive, annoying, and timeconsuming. For an e-mail service provider, spam e-mail representstangible costs in terms of storage and bandwidth usage. These costs maybe substantial when large numbers of spam e-mails are sent.

SUMMARY

In one aspect, techniques for handling a communication from a sender toan intended recipient are described. A communication is received from asender. The communication is directed to an intended recipient. Thesender of the communication and the intended recipient of thecommunication are identified. A determination is made as to whether thesender and the intended recipient are linked by less than a thresholdnumber of degrees of separation. Based at least in part on whether thesender and the intended recipient are linked by less than the thresholdnumber of degrees of separation, a determination is made as to whetherthe communication is a spam communication.

Implementations of this aspect may include one or more of the followingfeatures. For example, determining whether the sender and the intendedrecipient are linked by less than the threshold number of degrees ofseparation may include determining whether the sender and the intendedrecipient are linked by at least one intermediary entity. How manyintermediary entities are needed to link the sender to the intendedrecipient may be determined and whether the communication is a spamcommunication may be determined based on how many intermediary entitiesare needed to link the sender to the intended recipient.

Determining whether the sender is linked to the intended recipient by atleast one intermediary entity may include accessing a contact list ofthe intended recipient to determine at least one contact on the contactlist. Accessing a contact list of the intended recipient may includeaccessing a contact list with communication identifiers related to thesame or a different type of communication than the communication fromthe sender to the intended recipient. For example, the contact list ofthe intended recipient may include an address book; a buddy list; apersonal phone book; or a white list. The communication may be, forinstance, an e-mail message; an instant message; an SMS message; or atelephone call.

Determining whether the communication is a spam communication mayinclude determining a spam rating for the communication based on whetherthe sender is linked to the intended recipient by less than a thresholdnumber of degrees of separation; and designating the communication asspam or blocking the communication when the spam rating exceeds aclassification threshold. How many intermediary entities link the senderto the intended recipient may be determined and determining the spamrating may include determining the spam rating for the communicationbased on how many intermediary entities link the sender to the intendedrecipient.

The communication may be exempted from the determination of whether thecommunication is a spam communication when less than M intermediaryentities link the sender to the intended recipient or when greater thanM+X entities link the sender to the intended recipient. Whether thecommunications is a spam communication may be determined when betweenM+1 and M+X intermediary entities link the sender and the intendedrecipient.

Determining whether the sender and the intended recipient are linked byat least one intermediary entity may include accessing a contact list ofthe intended recipient to determine a first contact on the intendedrecipient's contact list; and accessing a contact list of the firstcontact to determine a second contact on the first contact's contactlist.

In another aspect, a communication from a sender is received. Thecommunication is directed to an intended recipient. The sender and theintended recipient of the communication are identified. A contact listof the intended recipient is accessed. The contact list containscommunication identifiers related to a different type of communicationthan the communication from the sender. Whether the sender and theintended recipient are linked by less than a threshold number of degreesof separation is determined based on the communication identifiers inthe contact list that are related to a different type of communicationthan the communication from the sender. The communication is handledbased on whether the sender and the intended recipient are linked byless than the threshold number of degrees of separation.

Implementations of this aspect may include one or more of the followingfeatures. For example, determining whether the sender and the intendedrecipient are linked by less than the threshold number of degrees ofseparation may include determining whether the sender and the intendedrecipient are linked by at least one intermediary entity based on thecontact list. The communication may be an e-mail message and thecommunication identifiers in the contact list may relate to acommunication type other than e-mail messages. The communication may bean instant message and the communication identifiers in the contact listrelate to a communication type other than instant messages. Thecommunication may be an SMS message and the communication identifiers inthe contact list may relate to a communication type other than SMSmessages. The communication may be a telephone call and thecommunication identifiers in the contact list may relate to acommunication type other than telephone calls.

How many intermediary entities are needed to link the sender to theintended recipient may be determined. Whether the communication is aspam communication may be based on how many intermediary entities areneeded to link the sender to the intended recipient.

The contact list of the intended recipient may include an address book;a buddy list; a personal phone book; or a white list. Handling thecommunication may include using whether the sender and the intendedrecipient are linked by less than a threshold number of degrees ofseparation to determine if the communication is spam.

Handling the communication may include exempting the communication fromfiltering if the sender is linked to the intended recipient. Handlingthe communication may include determining a spam rating for thecommunication based on whether the sender is linked to the intendedrecipient by less than a threshold number of degrees of separation; anddesignating the communication as spam or blocking the communication whenthe spam rating exceeds a classification threshold. The spam rating forthe communication may be determined based on how many intermediaryentities link the sender to the intended recipient.

Handling the communication may include handling the communicationdifferently based on how many intermediary entities link the sender tothe intended recipient. Handling the communication differently mayinclude exempting the communication from filtering if less than Mintermediary entities link the sender to the intended recipient;subjecting the communication to filtering if between M+1 and M+Xintermediary entities link the sender to the intended recipient; and/ordiscarding the communication if greater than M+X entities link thesender to the intended recipient.

Determining whether the sender and the intended recipient are linked byat least one intermediary entity may include determining a first contacton the contact list of the intended recipient; and accessing a contactlist of the first contact to determine a second contact on the firstcontact's contact list.

Handling the communication may include invoking a knock-knock interfacewhen the sender and the intended recipient are not linked by less thanthe threshold number of degrees of separation.

Implementations of the described techniques may include hardware, amethod or process, or computer software on a computer-accessible medium.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features will beapparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an exemplary networked computing environmentthat supports e-mail communications and in which spam filtering may beperformed.

FIG. 2 is an illustration showing an exemplary address book that may bedisplayed to a user of an e-mail client program.

FIG. 3 is an illustration showing an interface that allows an e-mailclient program user to add contacts to a white list.

FIG. 4 is a flow chart of a process for using an e-mail sender's degreesof separation from a mail recipient to aid in spam filtering.

FIG. 5 is a flow chart of an alternate process for using a sender'sdegrees of separation from a mail recipient to aid in spam filtering.

FIG. 6 is an illustration showing an exemplary interface that may beused to allow a user to adjust preferences with regard to the degrees ofseparation feature.

DETAILED DESCRIPTION

In general, the degree of separation between a sender and an intendedrecipient is used to inform filtering of a communication sent from thesender to the intended recipient. The degree of separation between twoentities describes a relationship between those entities.

Typically, user contact lists (e.g., address book, buddy list, and/orwhite list) are evaluated to determine the number of degrees (or hops)that are required to link or relate two users.

For example, recipient A may list user B in recipient A's address book,user B may list user C in user B's address book, and user C may listsender D in user C's address book. Here, sender D is linked to recipientA by two degrees of separation (with user B as the first degree and userC as the second degree). Recipient A is related to user C by one degreeof separation (user B) and user B is separated from sender D by onedegree of separation (user C). Recipient A and user B, users B and C,and user C and sender D are each respectively separated by zero degreesof separation.

The connectedness or lack of connectedness is used, possibly along withthe degrees of separation, to aid the handling of communications sent tothe recipient by the sender. For instance, handling may be informedbased on: (1) whether a sender and a recipient are connected (i.e., thesender and the recipient are known to each other or the sender is knownto the recipient); and (2) if they are connected, the number of degrees,hops or intermediaries required to link or relate the sender to therecipient.

The following description more fully describes these techniques asapplied to e-mail spam filtering. However, the techniques may be appliedto other communication media and to other filtering applications.

FIG. 1 illustrates an exemplary networked computing environment 100 thatsupports e-mail communications and in which spam filtering may beperformed. Computer users are distributed geographically and communicateusing client systems 110 a and 110 b. Client systems 110 a and 110 b areconnected to Internet service provider (ISP) networks 120 a and 120 b,respectively. Clients 110 a and 110 b may be connected to the respectiveISP networks 120 a and 120 b through various communication channels suchas a modem connected to a telephone line (using, for example, serialline internet protocol (SLIP) or point-to-point protocol (PPP)) or adirect network connection (using, for example, transmission controlprotocol/internet protocol (TCP/IP)). E-mail servers 130 a and 130 balso are connected to ISP networks 120 a and 120 b, respectively. ISPnetworks 120 a and 120 b are connected to a global network 140 (e.g.,the Internet) such that a device on one ISP network 120 a or 120 b cancommunicate with a device on the other ISP network 120 a or 120 b. Forsimplicity, only two ISP networks 120 a and 120 b have been illustratedas connected to Internet 140. However, there may be a large number ofsuch ISP networks connected to Internet 140. Likewise, many e-mailservers and many client systems may be connected to each ISP network.

Each of the client systems 110 a and 110 b and the e-mail servers 130 aand 130 b may be implemented using, for example, a general-purposecomputer capable of responding to and executing instructions in adefined manner, a personal computer, a special-purpose computer, aworkstation, a server, a device, a component, or other equipment or somecombination thereof capable of responding to and executing instructions.Client systems 110 a and 110 b and e-mail servers 130 a and 130 b mayreceive instructions from, for example, a software application, aprogram, a piece of code, a device, a computer, a computer system, or acombination thereof, which independently or collectively directoperations. These instructions may take the form of one or morecommunications programs that facilitate communications between the usersof client systems 110 a and 110 b. Such communications programs mayinclude, for example, e-mail programs, IM programs, file transferprotocol (FTP) programs, or voice-over-IP (VoIP) programs. Theinstructions may be embodied permanently or temporarily in any type ofmachine, component, equipment, storage medium, or propagated signal thatis capable of being delivered to a client system 110 a and 110 b or thee-mail servers 130 a and 130 b.

Each of client systems 110 a and 110 b and e-mail servers 130 a and 130b includes a communications interface (not shown) used by thecommunications programs to send communications. The communications mayinclude e-mail, audio data, video data, general binary data, or textdata (e.g., data encoded in American Standard Code for InformationInterchange (ASCII) format).

Examples of ISP networks 120 a and 120 b include Wide Area Networks(WANs), Local Area Networks (LANs), analog or digital wired and wirelesstelephone networks (e.g., a Public Switched Telephone Network (PSTN), anIntegrated Services Digital Network (ISDN), or a Digital Subscriber Line(xDSL)), or any other wired or wireless network.

Networks 120 a and 120 b may include multiple networks or subnetworks,each of which may include, for example, a wired or wireless datapathway.

Each of e-mail servers 130 a and 130 b may handle e-mail for thousandsor more e-mail users connected to an ISP network 120 a or 120 b. Eache-mail server may handle e-mail for a single e-mail domain (e.g.,aol.com) or for multiple e-mail domains. In addition, each e-mail servermay be composed of multiple, interconnected computers working togetherto provide e-mail service for e-mail users of the corresponding ISPnetwork.

An e-mail user, such as a user of client system 110 a or 110 b,typically has one or more e-mail accounts on an e-mail server 130 a or130 b. Each account corresponds to an e-mail address. Each account(otherwise referred to as a user mailbox) may have one or more foldersin which e-mail is stored. E-mail sent to one of the e-mail user'se-mail addresses is routed to the corresponding e-mail server 130 a or130 b and placed in the account that corresponds to the e-mail addressto which the e-mail was sent. The e-mail user then uses, for example, ane-mail client program executing on client system 110 a or 110 b toretrieve the e-mail from e-mail server 130 a or 130 b and view thee-mail. The e-mail client program may be, for example, a web browser (inthe case of HTML mail), a stand-alone e-mail program, or an e-mailprogram that is part of an integrated suite of applications.

The e-mail client programs executing on client systems 110 a and 110 balso may allow one of the users to send e-mail to an e-mail address. Forexample, the e-mail client program executing on client system 110 a mayallow the e-mail user of client system 110 a (the sender) to compose ane-mail message and address the message to a recipient address, such asan e-mail address of the user of client system 110 b. When the senderindicates the e-mail is to be sent to the recipient address, the e-mailclient program executing on client system 110 a communicates with e-mailserver 130 a to handle the sending of the e-mail to the recipientaddress. For an e-mail addressed to an e-mail user of client system 110b, for example, e-mail server 130 a sends the e-mail to e-mail server130 b. E-mail server 130 b receives the e-mail and places the e-mail inthe account that corresponds to the recipient address. The user ofclient system 110 b may then retrieve the e-mail from e-mail server 130b, as described above.

To aid a user in sending e-mails, many e-mail client programs or otherprograms allow a user to maintain an address book. An address book is alist of the user's contacts along with their contact information. Anaddress book may contain a contact's e-mail address, instant messagingscreenname, street address, and/or telephone number(s). The address bookmay be stored on the client system or on a server, and may be accessedby the client program.

FIG. 2 illustrates an exemplary address book 200 that may be displayedto a user of an e-mail client program. Address book 200 includes a listbox 210 that contains a list 215 of the user's contacts. Only a singlecontact, John Smith, is shown in contact list 215, though a contact listmay contain multiple entries. When a contact in contact list 215 isselected, the contact's information 225 is shown in a box 220. Theinformation contains, for example, the contact's name, the contact'sscreenname, and the contact's e-mail address.

In an e-mail environment such as that shown in FIG. 1, a spammertypically uses an e-mail client program to send similar spam e-mails tohundreds, if not thousands, of e-mail recipients. For example, a spammermay target hundreds of recipient e-mail addresses serviced by e-mailserver 130 b on ISP network 120 b, and may maintain the list of targetedrecipient addresses as a distribution list. The spammer may use thee-mail client program to compose a spam e-mail and may instruct thee-mail client program to use the distribution list to send the spame-mail to the recipient addresses. The e-mail then is sent to e-mailserver 130 b for delivery to the recipient addresses.

Filtering traditionally has been used to eliminate or at least reducesome spam e-mail. Filtering may be done on the server-side, e.g. ate-mail server 130 b, or on the client-side, e.g. at client 110 b. Thus,a spam filter may be located on the server or the client. Whereverlocated, the spam filter may analyze e-mail coming into the server orclient to determine whether any of the e-mail is spam. Once the filterdesignates a piece of e-mail as spam, the e-mail is treated accordingly.For example, the spam e-mail may be deleted or placed in a specific spamfolder.

A spam filter may be implemented using a number of techniques. Onetechnique that has been used is simple text filtering, in which ane-mail's headers and/or the e-mail body is searched for simple textstrings or regular expressions and the e-mail is classified as spambased on whether the string or expression is present. Other techniquesanalyze word or other features of an e-mail to develop a rating orprobability measure of the likelihood that the e-mail is spam, and thencompare the rating or measure to a classification threshold. If therating or measure exceeds the threshold, the e-mail is designated asspam. The techniques used to develop the ratings may be, for example,heuristic or Bayesian based.

The spam filter also may employ so-called white lists and/or blacklists. A black list is a list of e-mail domains, specific e-mailaddresses, or IP addresses that are considered to be a source of spam.Any e-mail received from a blacklisted domain, e-mail address or IPaddress is designated by the filter as spam.

A white list typically is used to help ensure that legitimate e-mail isdelivered to the recipient. Similar to a black list, a white list is alist of e-mail domains, specific e-mail addresses, or IP addresses. Theitems on a white list, however, generally are considered to be sourcesof legitimate e-mail. Consequently, any e-mail received from a source onthe white list is designated as legitimate e-mail (i.e., non-spam) andexempted from further filtering.

FIG. 3 illustrates an interface 300 that allows an e-mail client programuser to add contacts to a white list. Interface 300 includes a list box310 that contains a list of contacts 315. Interface 300 also includes anedit box 320 and “Add” button 330 for adding additional contacts to list315. A radio button 340 is included in interface 300 to allow the userto designate list 315 as a white list (i.e. to allow e-mail from thelisted contacts to be delivered without being subjected to spamfiltering).

An e-mail sender's degree of separation from a mail recipient also maybe used to aid in spam filtering. The “degree of separation” representsa metric used to quantify whether/how the recipient is linked to thesender through intermediary people or other entities. For example, arecipient may know a first user (first degree of separation) and thefirst user may know a second user (second degree of separation) whoknows the sender of an e-mail. In this case, the sender is separatedfrom the recipient by two degrees of separation (i.e., by twointermediate contacts). A level of “trust” or “legitimacy” about asender's communication can be inferred by looking at whether the senderis linked to a recipient through the recipient's contacts, therecipient's contacts' contacts, or otherwise, with the level of trusttypically diminishing as the number of degrees of separation increases.For instance, a system or user may consider a communication based onmore degrees of separation between the sender and recipient as lesslikely to be legitimate or trusted than one with fewer degrees ofseparation.

A trusted list of contacts linked to a user/recipient may be developedfor use with a spam filter when filtering. The trusted list may bedeveloped, for example, by evaluating a contact list for the intendedrecipient that lists the intended recipient's contacts as more fullydescribed below. The contact list may contain communication identifiersrelated to the type of communication that is received (e.g., a buddylist may be accessed when the type of communication is an instantmessage, while an address book may be referenced when the type ofcommunication being filtered is an e-mail communication or telephonecall), or the contact list may contain communication identifiers relatedto a different type of communication than the one that is sent (e.g., abuddy list may be accessed when the communication is an e-mail), or acombination of similar and different types of contact lists may beaccessed. Further, a single contact list may have both communicationidentifiers related to the type of communication received andcommunication identifiers related to a different type of communicationthan the one received. Whether a contact is linked to an intendedrecipient may be based on communication identifiers related to the typeof communication received or may be based on communication identifiersrelated to a different type of communication than the one received.

Thus, for example, a contact may be determined as linked to an intendedrecipient based on an IM screen names. This contact, however, may beplaced in a trusted list that is used for e-mail communications. Inother words, a contact may be determined to be linked to the intendedrecipient based on one type of communication, and this link is used forother types of communications. The link based on IM screen names may bedetermined, for instance, by accessing a buddy list of the intendedrecipient or by accessing a central contact list that contains e-mailaddresses and IM screen names.

The trusted list may simply contain a communication identifier (e.g.,e-mail address or screenname) for the linked contacts, or the trustedlist also may contain the degrees of separation between the user and thelinked contacts, depending on how the trusted list is used to facilitatespam filtering. The trusted list also may contain other informationabout a linked contact. The following is an example of a trusted listthat contains a communication identifier and the degrees of separationfor each linked contact: Trusted List Screennames Degrees of Separationrandomcontact 2 Jsmith 3 internetann 1 chattinchuck 4

Depending on the spam filtering techniques employed by the spam filter,the trusted list may be used simply as a white list to exempt from spamfiltering those e-mails from the linked contacts. Similarly, the trustedlist may be used simply as a white list to allow only communicationsfrom those entities on the white list to be delivered to the intendedrecipient, with all other communications being prevented from reachingthe intended recipient.

Alternatively, the presence or absence of a sender on the trusted list(and possibly the sender's degrees of separation) may be considered afeature of an e-mail when determining whether the e-mail is spam. Forexample, for a spam filter that heuristically develops a rating of thelikelihood that an e-mail is spam, the presence in the trusted list maydecrease the rating, with lower degrees of separation decreasing therating more than higher degrees of separation. For a Bayesian spamfilter, the presence or absence on the trusted list, along with thedegrees of separation, may be considered a feature for both training andclassification. The degrees of separation may be used with otherfeatures of the e-mail to determine a spam rating. The other featuresmay include, for example, origin IP address, origin domain, mime-typescontained in the e-mail, sender's address, and specific words in thebody of the e-mail.

Alternatively, or additionally, e-mail may be treated differently basedon the sender's degrees of separation. For example, e-mail whose senderis within 1 to M degrees of separation may be exempted from filtering,e-mail whose sender is within M+1 to M+X degrees of separation may betreated as unknown and consequently filtered, and e-mail whose sender isnot linked or is linked by a degree of separation greater than M+X maybe automatically discarded as spam. Other ways of treating the e-mailare possible, as are other ways of dividing up the relevant degrees ofseparation.

FIG. 4 is a flow chart of a process 400 for using an e-mail sender'sdegrees of separation from a mail recipient to aid in spam filtering. Alist of contacts is maintained for the recipient (410). The list ofcontacts may be any personally maintained list, for example, an addressbook, a buddy list for instant messaging, and/or a white list. The restof process 400 will be described using an address book as an example ofa list of contacts.

The contacts in the recipient's address book are added to a trusted listof the recipient (420). If the trusted list contains, for example,e-mail addresses, but the contact list only contains screennames, thenthe contacts' e-mail addresses may be looked-up using, for example, adatabase that correlates information such as a user's e-mail address andIM screennames.

Next, the contacts linked to the recipient (i.e., up to a desired degreeof separation) are identified and added to the trusted list. To do so,the address books of each contact in the recipient's address book areaccessed (430). The contacts in the recipient's contacts' address books(i.e., the contacts separated by one degree) then are added to thetrusted list (440). If another degree of separation is desired (450),the degree of separation is incremented (460) such that the addressbooks of the contacts that are separated from the recipient by onedegree are accessed (430) and the contacts in those address books areadded to the trusted list (440). When a contact is added to the trustedlist, the contact's degree of separation from the recipient also may beadded. The addition of contacts continues until the desired degree ofseparation is reached (450). Once the desired degree of separation hasbeen reached, the trusted list is input to the spam filter for use infiltering spam (470).

Process 400 may be performed before an e-mail is received and thetrusted list may be stored for use with the spam filter. Alternatively,process 400 may be performed whenever an e-mail is received.

Process 400 may result in the trusted list not being updated when anyusers related to the intended recipient update their contact lists. Thatis, if a user related to the intended recipient adds a contact to theuser's contact list, the new contact may not be reflected in theintended recipient's trusted list. This situation may not be overlydetrimental, particularly in implementations where the trusted list isused as a white list to exempt certain e-mails from spam filtering.However, repeating process 400 on a periodic or aperiodic basis maymitigate this situation. Another manner of mitigating this situation isto use an update system in which changes to contact lists are trackedand trusted lists are updated accordingly in an incremental fashion orby triggering an update or re-initiation of process 400 when an updateoccurs. The alternate process 500 illustrated in FIG. 5 also maymitigate such a situation.

FIG. 5 is a flow chart of an alternate process 500 for using a sender'sdegrees of separation from a mail recipient to aid in spam filtering.When an e-mail is received (510), the sender's address is retrieved fromthe e-mail (520). A search then is performed to determine the sender'sdegree of separation from the recipient (530). In one implementation, toperform the search, the contacts in the recipient's address book (i.e.,the contacts separated by zero degrees) are searched to determine if thesender is among those contacts. If not, then the address books of one ormore contacts in the recipient's address book are accessed and searchedto determine if the sender is among those contacts. If the sender is notamong those contacts, and another degree of separation is desired, thedegree of separation is incremented such that the address books of thecontacts that are separated from the recipient by one degree areaccessed and searched to determine if the sender is among thosecontacts. This continues until the desired degree of separation has beenreached. At that point, if the sender has not been located, then thesender is not considered to be linked to the recipient. An indication ofwhether the sender is linked to the intended recipient, and possiblyalso the sender's degree of separation from the intended recipient, areinput to a spam filter for use in determining whether the e-mail is spam(540).

Process 400 or process 500 may be implemented by the server, by theclient, or by a combination of both.

The contact lists of the users may be stored centrally or in adistributed fashion. For example, the techniques may be applied to anenvironment in which all of the users' contact lists are stored on asingle server (completely centralized), or on a single cluster ofservers owned by the same e-mail service provider (partiallycentralized/distributed).

The contact lists may be stored in a more fully distributed fashion bybeing stored on different servers owned by different e-mail serviceproviders (which may or may not adopt a standardized protocol forsharing information such as contact lists), or by being stored on eachclient system (i.e., each user's contact list is stored on the user'sclient system). If the contact lists are stored on the client (e.g., aclient running Microsoft Outlook), the accessing and searching of thecontacts' address books or other contact lists may be performed usingpeer-to-peer techniques. When contact lists are stored on the clients,privacy and security measures may be implemented, such as hashing thetrusted list or otherwise making it unreadable to the user, so that theuser can not determine who is listed in his or her contacts' lists orotherwise have access to someone's contact information that has not beenspecifically given to the user. For example, if a recipient has only onecontact in his or her contact list and only one degree of separation isused, then the recipient may be able to discern who that single contacthas on his or her contact list. Making the trusted list unreadable toits “owner” may eliminate this potential issue.

In a distributed environment in which different contact lists aremaintained on servers of different providers, a trusted group model maybe implemented to allow access to the different contact lists, asneeded, to develop the degrees of separation between a recipient and asender. For example, if the user of client system 110 b has an accounton e-mail server 130 b and the user's address book is maintained onserver 130 b, the user's address book (or the user's contacts' addressbooks) may include contacts with address books maintained on a serverowned by a different provider, such as, for example, server 130 a.Generally, the provider of server 130 a would not allow outside partiesto access the contact lists of its users. To implement the foregoingtechniques, however, a trusted group model may be developed that allowsserver 130 b to access the address books or other contact lists of theusers whose accounts are maintained on server 130 a. In this way, server130 b may be able to determine the linked contacts, even if some of thecontact lists are on server 130 a. Thus, for instance, e-mail serviceproviders such as America Online (AOL) and Hotmail may cooperate toallow access to users' contact lists so as to increase the effectivenessof the foregoing techniques. Also, for example, two corporations, eachrunning an e-mail server (e.g., a Microsoft Exchange server), acorporation and an ISP, or any two e-mail service providers maycooperate to allow access to users' contact lists.

Regardless of whether a client-side or server-side implementation isused, for some implementations the foregoing techniques may be limitedout of privacy or security concerns similar to those described abovewith regard to storing the contact lists at the client. For example, ifa recipient has only one contact in his or her contact list and only onedegree of separation is used, then the recipient may be able to discernwho that single contact has on his or her contact list if restrictionsare not applied.

The use of the foregoing techniques may be limited such that thetechniques are not performed when the number of contacts in arecipient's contact list is below a predetermined number. Also, theremay be a requirement that a minimum number of degrees of separation aresearched. Other limitations may include limiting a user's ability toperceive his or her trusted list. Preventing the user's ability toperceive or access the trusted list may be accomplished by preventingthe display of the trusted list, storing the trusted list remote fromthe user, or, as described above, storing the trusted list as a hash.

The foregoing techniques also may be limited such that a contact list isnot used when the contact list does not contain the recipient. In otherwords, the contact lists of users who do not include the recipient arenot used to determine contacts at the next level of separation. Forexample, if user A is a mail recipient, a user B that is in user A'saddress book may be indicated as a linked user. When user B's addressbook contains user A, user B's address book is used for the next degreeof separation, which results in a user C (who is in user B's addressbook) as being linked to user A. However, because user C's address bookdoes not contain user A, user C's address book is not used when a searchis done for the next degree of separation.

The techniques are described as being applied to e-mail spam filtering.However, the techniques may be used for spam filtering of communicationsin other communication media, including both text and non-text media.For example, the techniques may be applied to instant messaging. In suchan environment, an instant messaging buddy list or an address book maybe used as the contact list, and the trusted list may contain thescreennames of linked contacts. The trusted list may be input into aspam filter that prevents spam instant messages. Another example of anenvironment in which the foregoing techniques may be implemented isshort messaging service (SMS) communications used in cell phones. Inthis case, a phone book for the cell phone may be used as the contactlist. As another example, these techniques may be used to filtertelephone calls based on a user's contact list, such as a personal phonebook or an address book, particularly if the telephone calls are carriedover packet networks such as the Internet.

The above techniques also may be extended to apply to the generalhandling, classification, or filtering of communications. For example, arecipient may want messages from senders who are linked to the recipientto be classified as important, while other messages are classified aslow priority. Similarly, a Bayesian classifier may be used to classifyreceived e-mail into classes other than spam. The Bayesian classifiermay be trained with a set of e-mail that includes information aboutwhether a sender of the e-mail is linked to the recipient and, if so, byhow many degrees. The Bayesian classifier then may use the informationwhen classifying an unknown e-mail.

As another example of general handling of communications, the handlingin an instant messaging implementation (or other implementations) mayinclude bypassing or invoking a “knock-knock” interface. At times, whena sender sends an intended recipient an instant message, instead ofreceiving the instant message right away, the intended recipient'sinstant messaging program invokes a “knock-knock” interface. Theinterface typically informs the intended recipient that the sender istrying to instant message him or her, identifies the sender (e.g., bydisplaying the screen name of the sender), and provides the intendedrecipient with an option of accepting the message. If the intendedrecipient indicates that he or she wishes to accept the instant message,it is delivered to the intended recipient and displayed to the intendedrecipient. On the other hand, if the intended recipient indicates he orshe would not like to receive the message, the message is not providedto the intended recipient and, for example, may be discarded. In someimplementations, the sender also is placed on a block list when theintended recipient indicates he or she does not want to receive aninstant message from the sender. The block list is used to preventfurther instant message communications from users on the block listwithout bothering the intended recipient, i.e., instant messages fromusers on the block list are automatically ignored without asking theintended recipient whether he or she wants to receive them.

The trusted list may be used to determine when to invoke a knock-knockinterface. To do so, whether a knock-knock interface is invoked maydepend on the number of degrees of separation between the sender and theintended recipient. In one implementation, instant messages from sendersless than or equal to n degrees away from the intended recipient areprovided to the intended recipient automatically without a knock-knockinterface being invoked, while a knock-knock interface is invoked forinstant messages from senders greater than n degrees away from theintended recipient. Alternatively, instant messages from senders within1 to M degrees may be provided to the intended recipient without aknock-knock interface being invoked, instant messages from senderswithin M+1 to N degrees may cause a knock-knock to be invoked, whileinstant messages from senders greater than N degrees away may beautomatically discarded without invoking a knock-knock interface orotherwise informing the intended recipient.

The above techniques have been described as creating a “trusted” list.However, these techniques could be used to source a “non-trusted” listby adding the black lists (or other lists denoting untrusted senders) oflinked contacts to a non-trusted list for the intended recipient, atleast up to a threshold degree of separation. The non-trusted list maythen, for example, be used as a black list, or may be a factor for spamfiltering.

Creating such a non-trusted list may be used in conjunction withdeveloping the trusted list. For example, for each or a subset of thecontacts added to the trusted list, the entities on the added contacts'black lists (or other lists denoting untrusted senders) can be placed onthe intended recipient's non-trusted list. As another example, when acontact's contact list is accessed and added to the trusted list, thecontact's list of untrusted senders also may be accessed and added tothe non-trusted list.

FIG. 6 illustrates an exemplary interface 600 that may be used to allowa user to adjust preferences with regard to the degrees of separationfeature. Some implementations may provide a user the ability to decidewhether degrees of separation will be used, and, if so, how many degreesshould be used. Exemplary interface 600 includes a text 605 thatexplains to the user that the user may decide to have his or her whitelist populated using degrees of separation and that the user may selecthow many degrees to use. Text 605 includes a hyperlinked portion 610that, when selected by the user, invokes an interface (not shown) thatprovides information about degrees of separation.

Interface 600 also has a check box 615 that allows a user to selectwhether degrees of separation should be used to develop his or her whitelist. When check box 615 is not checked, degrees of separation will notbe used. When check box 615 is checked, degrees of separation will beused.

Interface 600 additionally has an edit box 620 that allows a user toselect how many degrees will be used to develop the white list. Whencheck box 615 is not checked, edit box 620 becomes inactive and isgrayed out. When check box 615 is checked, however, edit box 620 becomesactive and the user is able to enter the number of degrees to be used.

An OK button 625 is available on interface 600 to allow the user toindicate that the preferences selected in interface 600 should be saved.A Cancel button 630 cancels the preferences without saving them.

Other implementations may provide varying levels of user control. Forinstance, the user may be able to select whether white lists (or othertrusted lists) are used, but without any control over whether degrees ofseparation are used. That is, the system may automatically use degreesof separation when the user chooses to use white lists or other trustedlists. Alternatively, for example, a system may use the white lists orother trusted lists and degrees of separation without providing the usercontrol over either.

The techniques described above are not limited to any particularhardware or software configuration. Rather, they may be implementedusing hardware, software, or a combination of both. The methods andprocesses described may be implemented as computer programs that areexecuted on programmable computers comprising at least one processor andat least one data storage system. The programs may be implemented in ahigh-level programming language and may also be implemented in assemblyor other lower level languages, if desired.

Any such program will typically be stored on a computer-usable storagemedium or device (e.g., CD-Rom, RAM, or magnetic disk). When read intothe processor of the computer and executed, the instructions of theprogram cause the programmable computer to carry out the variousoperations described above.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherimplementations are within the scope of the following claims.

1. A method for handling a communication from a sender to an intendedrecipient, the method comprising: receiving a communication from asender, wherein the communication is directed to an intended recipient;identifying the sender of the communication; identifying the intendedrecipient of the communication; determining whether the sender and theintended recipient are linked by less than a threshold number of degreesof separation; and determining whether the communication is a spamcommunication based at least in part on whether the sender and theintended recipient are linked by less than the threshold number ofdegrees of separation.
 2. The method of claim 1 wherein determiningwhether the sender and the intended recipient are linked by less thanthe threshold number of degrees of separation includes determiningwhether the sender and the intended recipient are linked by at least oneintermediary entity.
 3. The method of claim 2 further comprising:determining how many intermediary entities are needed to link the senderto the intended recipient; and determining whether the communication isa spam communication based on how many intermediary entities are neededto link the sender to the intended recipient.
 4. The method of claim 2wherein determining whether the sender is linked to the intendedrecipient by at least one intermediary entity comprises accessing acontact list of the intended recipient to determine at least one contacton the contact list.
 5. The method of claim 4 wherein accessing acontact list of the intended recipient comprises accessing a contactlist with communication identifiers related to a different type ofcommunication than the communication from the sender to the intendedrecipient.
 6. The method of claim 4 wherein accessing a contact list ofthe intended recipient comprising accessing a contact list withcommunication identifiers related to the type of communication thatincludes the communication from the sender to the recipient.
 7. Themethod of claim 4 wherein the contact list of the intended recipientcomprises an address book.
 8. The method of claim 4 wherein the contactlist of the intended recipient comprises a buddy list.
 9. The method ofclaim 4 wherein the contact list of the intended recipient comprises apersonal phone book.
 10. The method of claim 4 wherein the contact listof the intended recipient comprises a white list.
 11. The method ofclaim 2 wherein the communication is an e-mail message.
 12. The methodof claim 2 wherein the communication is an instant message.
 13. Themethod of claim 2 wherein the communication is an SMS message.
 14. Themethod of claim 2 wherein the communication is a telephone call.
 15. Themethod of claim 2 wherein determining whether the communication is aspam communication further comprises: determining a spam rating for thecommunication based on whether the sender is linked to the intendedrecipient by less than a threshold number of degrees of separation; anddesignating the communication as spam or blocking the communication whenthe spam rating exceeds a classification threshold.
 16. The method ofclaim 15 further comprising determining how many intermediary entitieslink the sender to the intended recipient; wherein determining the spamrating further comprises determining the spam rating for thecommunication based on how many intermediary entities link the sender tothe intended recipient.
 17. The method of claim 2 further comprising:determining how many intermediary entities link the sender to theintended recipient; exempting the communication from the determinationof whether the communication is a spam communication when less than Mintermediary entities link the sender to the intended recipient or whengreater than M+X entities link the sender to the intended recipient; andwherein determining whether the communication is a spam communicationcomprises determining whether the communications is a spam communicationwhen between M+1 and M+X intermediary entities link the sender and theintended recipient.
 18. The method of claim 2 wherein determiningwhether the sender and the intended recipient are linked by at least oneintermediary entity comprises: accessing a contact list of the intendedrecipient to determine a first contact on the intended recipient'scontact list; and accessing a contact list of the first contact todetermine a second contact on the first contact's contact list.
 19. Acomputer-usable medium storing a computer program for handling acommunication from a sender to an intended recipient, the computerprogram comprising instructions for causing a computer to: receive acommunication from a sender, wherein the communication is directed to anintended recipient identify the sender of the communication; identifythe intended recipient of the communication; determine whether thesender and intended recipient are linked by less than a threshold numberof degrees of separation; and determine whether the communication is aspam communication based at least in part on whether the sender andintended recipient are linked by less than a threshold number of degreesof separation.
 20. The medium of claim 19 wherein, to determine whetherthe sender and intended recipient are linked by less than a thresholdnumber of degrees of separation, the program comprises instructions forcausing the computer to determine whether the sender and the intendedrecipient are linked by at least one intermediary entity.
 21. The mediumof claim 20 further comprising instructions for causing the computer to:determine how many intermediary entities are needed to link the senderto the intended recipient; and determine whether the communication is aspam communication based on how many intermediary entities are needed tolink the sender to the intended recipient.
 22. The medium of claim 20wherein, to determine whether the sender is linked to the intendedrecipient by at least one intermediary entity, the computer programcomprises instructions for causing a computer to access a contact listof the intended recipient to determine at least one contact on theintended recipient's contact list.
 23. The medium of claim 22 wherein,to access a contact list of the intended recipient, the computer programcomprises instructions for causing a computer to access a contact listrelated to a different type of communication than the communication fromthe sender to the intended recipient.
 24. The medium of claim 22wherein, to access a contact list of the intended recipient, thecomputer program comprises instructions for causing a computer to accessa contact list related to the type of communication from the sender. 25.The medium of claim 22 wherein the contact list of the intendedrecipient comprises an address book.
 26. The medium of claim 22 whereinthe contact list of the intended recipient comprises a buddy list. 27.The medium of claim 22 wherein the contact list of the intendedrecipient comprises a personal phone book.
 28. The medium of claim 22wherein the contact list of the intended recipient comprises a whitelist.
 29. The medium of claim 20 wherein the communication is an e-mailmessage.
 30. The medium of claim 20 wherein the communication is aninstant message.
 31. The medium of claim 20 wherein the communication isan SMS message.
 32. The medium of claim 20 wherein the communication isa telephone call.
 33. The medium of claim 20 wherein, to determinewhether the communication is a spam communication, the computer programcomprises instructions for causing a computer to: determine a spamrating for the communication based on whether the sender is linked tothe intended recipient by less than a threshold number of degrees ofseparation; and designate the communication as spam or blocking thecommunication when the spam rating exceeds a classification threshold.34. The medium of claim 33 further comprising instructions for causing acomputer to: determine how many intermediary entities link the sender tothe intended recipient; and wherein, to determine the spam rating, thecomputer program comprises instructions for causing a computer todetermine the spam rating for the communication based on how manyintermediary entities link the sender to the intended recipient.
 35. Themedium of claim 20 further comprising instructions for causing acomputer to: determine how many intermediary entities link the sender tothe intended recipient; exempt the communication from the determinationof whether the communication is a spam communication when less than Mintermediary entities link the sender to the intended recipient or whengreater than M+X entities link the sender to the intended recipient; andwherein determining whether the communication is a spam communicationcomprises determining whether the communication is a spam communicationwhen between M+1 and M+X intermediary entities link the sender and theintended recipient.
 36. The medium of claim 20 wherein, to determinewhether the sender and intended recipient are linked by at least oneintermediary entity, the computer program comprises instructions forcausing a computer to: access a contact list of the intended recipientto determine a first contact on the intended recipient's contact list;and access a contact list of the first contact to determine a secondcontact on the first contact's contact list.
 37. An apparatus forhandling a communication from a sender to an intended recipient, theapparatus comprising: means for receiving a communication from a sender,wherein the communication is directed to an intended recipient; meansfor identifying the sender of the communication; means for identifyingthe intended recipient of the communication; means for determiningwhether the sender and intended recipient are linked by less than athreshold number of degrees of separation; and means for determiningwhether the communication is a spam communication based at least in parton whether the sender and intended recipient are linked by less than athreshold number of degrees of separation.
 38. The apparatus of claim 37wherein the means for determining whether the sender and intendedrecipient are linked by less than a threshold number of degrees ofseparation includes means for determining whether the sender andintended recipient are linked by at least one intermediary entity. 39.The apparatus of claim 38 wherein the means for determining whether thesender is linked to the intended recipient comprises means for accessinga contact list of the intended recipient to determine at least onecontact on the intended recipient's contact list.
 40. A method forhandling a communication from a sender to an intended recipient, themethod comprising: receiving a communication from a sender, wherein thecommunication is directed to an intended recipient; identifying thesender of the communication; identifying the intended recipient of thecommunication; accessing a contact list of the intended recipient thatcontains communication identifiers related to a different type ofcommunication than the communication from the sender; determiningwhether the sender and the intended recipient are linked by less than athreshold number of degrees of separation based on the communicationidentifiers in the contact list that are related to a different type ofcommunication than the communication from the sender; and handling thecommunication based on whether the sender and the intended recipient arelinked by less than the threshold number of degrees of separation. 41.The method of claim 40 wherein determining whether the sender and theintended recipient are linked by less than the threshold number ofdegrees of separation includes determining whether the sender and theintended recipient are linked by at least one intermediary entity basedon the contact list.
 42. The method of claim 41 wherein thecommunication is an e-mail message and the communication identifiers inthe contact list relate to a communication type other than e-mailmessages.
 43. The method of claim 41 wherein the communication is aninstant message and the communication identifiers in the contact listrelate to a communication type other than instant messages.
 44. Themethod of claim 41 wherein the communication is an SMS message and thecommunication identifiers in the contact list relate to a communicationtype other than SMS messages.
 45. The method of claim 41 wherein thecommunication is a telephone call and the communication identifiers inthe contact list relate to a communication type other than telephonecalls.
 46. The method of claim 41 further comprising: determining howmany intermediary entities are needed to link the sender to the intendedrecipient; and determining whether the communication is a spamcommunication based on how many intermediary entities are needed to linkthe sender to the intended recipient.
 47. The method of claim 40 whereinthe contact list of the intended recipient comprises an address book.48. The method of claim 40 wherein the contact list of the intendedrecipient comprises a buddy list.
 49. The method of claim 40 wherein thecontact list of the intended recipient comprises a personal phone book.50. The method of claim 40 wherein the contact list of the intendedrecipient comprises a white list.
 51. The method of claim 41 whereinhandling the communication comprises using whether the sender and theintended recipient are linked by less than a threshold number of degreesof separation to determine if the communication is spam.
 52. The methodof claim 41 wherein handling the communication further comprisesexempting the communication from filtering if the sender is linked tothe intended recipient.
 53. The method of claim 41 wherein handling thecommunication further comprises: determining a spam rating for thecommunication based on whether the sender is linked to the intendedrecipient by less than a threshold number of degrees of separation; anddesignating the communication as spam or blocking the communication whenthe spam rating exceeds a classification threshold.
 54. The method ofclaim 53 further comprising determining how many intermediary entitieslink the sender to the intended recipient; wherein determining the spamrating further comprises determining the spam rating for thecommunication based on how many intermediary entities link the sender tothe intended recipient.
 55. The method of claim 41 further comprisingdetermining how many intermediary entities link the sender to theintended recipient; wherein handling the communication compriseshandling the communication differently based on how many intermediaryentities link the sender to the intended recipient.
 56. The method ofclaim 55 wherein handling the communication differently comprises:exempting the communication from filtering if less than M intermediaryentities link the sender to the intended recipient; subjecting thecommunication to filtering if between M+1 and M+X intermediary entitieslink the sender to the intended recipient; and discarding thecommunication if greater than M+X entities link the sender to theintended recipient.
 57. The method of claim 41 wherein determiningwhether the sender and the intended recipient are linked by at least oneintermediary entity comprises: determining a first contact on thecontact list of the intended recipient; and accessing a contact list ofthe first contact to determine a second contact on the first contact'scontact list.
 58. The method of claim 40 wherein handling thecommunication includes invoking a knock-knock interface when the senderand the intended recipient are not linked by less than the thresholdnumber of degrees of separation.
 59. The method of claim 58 wherein thecommunication is an instant message.
 60. A computer-usable mediumstoring a computer program for handling a communication from a sender toan intended recipient, the computer program comprising instructions forcausing a computer to: receive a communication from a sender, whereinthe communication is directed to an intended recipient; identify thesender of the communication; identify the intended recipient of thecommunication; access a contact list of the intended recipient thatcontains communication identifiers related to a different type ofcommunication than the communication from the sender; determine whetherthe sender and the intended recipient are linked by less than athreshold number of degrees of separation based on the communicationidentifiers in the contact list that are related to a different type ofcommunication than the communication from the sender; and handle thecommunication based on whether the sender and the intended recipient arelinked by less than the threshold number of degrees of separation. 61.The medium of claim 60 wherein, to determine whether the sender and theintended recipient are linked by less than the threshold number ofdegrees of separation, the computer program comprises instructions forcausing a computer to determining whether the sender and the intendedrecipient are linked by at least one intermediary entity based on thecontact list.
 62. The medium of claim 61 wherein the communication is ane-mail message and the communication identifiers in the contact listrelate to a communication type other than e-mail messages.
 63. Themedium of claim 61 wherein the communication is an instant message andthe communication identifiers in the contact list relate to acommunication type other than instant messages.
 64. The medium of claim61 wherein the communication is an SMS message and the communicationidentifiers in the contact list relate to a communication type otherthan SMS messages.
 65. The medium of claim 61 wherein the communicationis a telephone call and the communication identifiers in the contactlist relate to a communication type other than telephone calls.
 66. Themedium of claim 61 wherein the computer program further comprisesinstructions for causing a computer to: determine how many intermediaryentities are needed to link the sender to the intended recipient; anddetermine whether the communication is a spam communication based on howmany intermediary entities are needed to link the sender to the intendedrecipient.
 67. The medium of claim 60 wherein the contact list of theintended recipient comprises an address book.
 68. The medium of claim 60wherein the contact list of the intended recipient comprises a buddylist.
 69. The medium of claim 60 wherein the contact list of theintended recipient comprises a personal phone book.
 70. The medium ofclaim 60 wherein the contact list of the intended recipient comprises awhite list.
 71. The medium of claim 61 wherein, to handle thecommunication, the computer program comprises instructions for causing acomputer to use whether the sender and the intended recipient are linkedby less than a threshold number of degrees of separation to determine ifthe communication is spam.
 72. The medium of claim 61 wherein, to handlethe communication, the computer program further comprises instructionsfor causing a computer to exempting the communication from filtering ifthe sender is linked to the intended recipient.
 73. The medium of claim61 wherein, to handle the communication, the computer program furthercomprises instructions for causing a computer to: determine a spamrating for the communication based on whether the sender is linked tothe intended recipient by less than a threshold number of degrees ofseparation; and designate the communication as spam or blocking thecommunication when the spam rating exceeds a classification threshold.74. The medium of claim 73 wherein the computer program furthercomprises instructions for causing a computer to determine how manyintermediary entities link the sender to the intended recipient; and todetermine the spam rating, the computer program further comprisesinstructions for causing a computer to determine the spam rating for thecommunication based on how many intermediary entities link the sender tothe intended recipient.
 75. The medium of claim 61 wherein the computerprogram further comprises instructions for causing a computer todetermine how many intermediary entities link the sender to the intendedrecipient; wherein, to handle the communication, the computer programfurther comprises instructions for causing a computer to handle thecommunication differently based on how many intermediary entities linkthe sender to the intended recipient.
 76. The medium of claim 75wherein, to handle the communication differently, the computer programfurther comprises instructions for causing a computer to: exempt thecommunication from filtering if less than M intermediary entities linkthe sender to the intended recipient; subject the communication tofiltering if between M+1 and M+X intermediary entities link the senderto the intended recipient; and discard the communication if greater thanM+X entities link the sender to the intended recipient.
 77. The mediumof claim 61 wherein, to determine whether the sender and the intendedrecipient are linked by at least one intermediary entity, the computerprogram further comprises instructions for causing a computer to:determine a first contact on the contact list of the intended recipient;and access a contact list of the first contact to determine a secondcontact on the first contact's contact list.
 78. The medium of claim 60wherein, to handle the communication, the computer program furthercomprises instructions for causing a computer to invoke a knock-knockinterface when the sender and the intended recipient are not linked byless than the threshold number of degrees of separation.
 79. The mediumof claim 78 wherein the communication is an instant message.
 80. Anapparatus for handling a communication from a sender to an intendedrecipient, the apparatus comprising: means for receiving a communicationfrom a sender, wherein the communication is directed to an intendedrecipient; means for identifying the sender of the communication; meansfor identifying the intended recipient of the communication; means foraccessing a contact list of the intended recipient that containscommunication identifiers related to a different type of communicationthan the communication from the sender; means for determining whetherthe sender and the intended recipient are linked by less than athreshold number of degrees of separation based on the communicationidentifiers in the contact list that are related to a different type ofcommunication than the communication from the sender; and means forhandling the communication based on whether the sender and the intendedrecipient are linked by less than the threshold number of degrees ofseparation.
 81. The apparatus of claim 80 wherein the means fordetermining whether the sender and the intended recipient are linked byless than the threshold number of degrees of separation includes meansfor determining whether the sender and the intended recipient are linkedby at least one intermediary entity based on the contact list.
 82. Theapparatus of claim 81 wherein the communication is an e-mail message andthe communication identifiers in the contact list relate to acommunication type other than e-mail messages.
 83. The apparatus ofclaim 81 wherein the communication is an instant message and thecommunication identifiers in the contact list relate to a communicationtype other than instant messages.
 84. The apparatus of claim 81 whereinthe communication is an SMS message and the communication identifiers inthe contact list relate to a communication type other than SMS messages.85. The apparatus of claim 81 wherein the communication is a telephonecall and the communication identifiers in the contact list relate to acommunication type other than telephone calls.